This invention relates to a foam control composition for use in aqueous foaming systems. More particularly, this invention relates to a composition consisting essentially of a silicone defoamer reaction product and a silicone glycol which is especially useful in controlling foam in highly acidic or highly basic systems operating at elevated temperatures. The present invention further relates to a composition consisting essentially of a silicone defoamer reaction product, a silicone glycol, and a low viscosity hydroxyl-endblocked polydiorganosiloxane.
The use of various silicone containing compositions as antifoams or defoamers is known. In this regard, it is well established that this art is highly unpredictable and slight modification can greatly alter performance of such compositions. Most of these compositions contain silicone fluid (usually dimethylpolysiloxane), often in combination with small amounts of silica filler. Additionally, these compositions may include various surfactants and dispersing agents in order to impart improved foam control or stability properties to the compositions.
Thus, for example, Rosen, in U.S. Pat. No. 4,076,648, teaches self-dispersible antifoam compositions consisting essentially of a lipophilic nonionic surface active agent homogeneously dispersed in a non-emulsified diorganopolysiloxane antifoam agent. This combination is said to promote dispersibility in water without the need for emulsification.
Kulkarni et al., in U.S. Pat. No. 4,395,352, improved upon the compositions disclosed by Rosen, cited supra, by limiting the viscosity of the dimethylpolysiloxane oil therein to the range of 5,000 to 30,000 cS at 25 C. Such a limitation, it is taught, unexpectedly resulted in improved efficiency in difficult-to-defoam aqueous systems, such as those which contain high concentrations of ionic surfactants and those which are very viscous.
Keil, in U.S. Pat. No. 3,784,479, discloses foam control compositions which consist essentially of a base oil selected from polyoxypropylene polymers, polyoxypropylene-polyoxyethylene copolymers or siloxane-glycol copolymers, a foam control agent, comprising a liquid dimethylpolysiloxane and silica filler, and a dispersing agent which consists of a copolymer of a siloxane resin and a polyoxyalkylene polymer. The contribution to the art in this case is stated to be improved compatibility with otherwise desirable diluents without resorting to emulsifying the foam control agent in water.
In a closely related patent, U.S. Pat. No. 3,984,347, Keil discloses foam control compositions which consist essentially of a base oil selected from polyoxypropylene polymers, polyoxypropylene-polyoxyethylene copolymers or siloxane-glycol copolymers, a foam control agent comprising a liquid dimethylpolysiloxane and silica filler and a siloxane copolymer dispersing agent. This time the dispersing agent consists of a copolymer of a dimethylpolysiloxane polymer and a polyoxyalkylene polymer. The same advantages as reported for U.S. Pat. No. 3,784,479, cited supra, were obtained.
A composition suitable for use as a defoamer in dyeing operations is taught by Colquhoun in U.S. Pat. No. 3,912,652. In this case, the composition consists of a copolymer of a dimethylpolysiloxane polymer and a polyoxyalkylene polymer combined with a lesser amount of a copolymer of a siloxane resin and a polyoxyalkylene polymer. Such compositions are stated to be particularly useful in jet dyeing operations since they are compatible with the dye carriers employed therein.
Japanese O.P.I. No. 139,107/81, published Oct. 30, 1981, teaches a self-emulsifying type defoaming agent which is said to have excellent foam-suppressing and breaking capability regardless of temperature and pH of a liquid to be treated and the storage period to which it is subjected. This agent is composed of a silicone copolymer having diorganosiloxane and organo-oxyalkylenesiloxane units in the copolymer chain.
A process for control of foaming in non-aqueous systems is disclosed by Lomas in U.S. Pat. No. 4,460,493. The compositions employed consist essentially of (1) at least one foam control agent, selected from polydimethylsiloxane or poly(methyl-3,3,3-trifluoropropyl)siloxane, which may optionally include a minor portion of a siloxane resin, (2) a dispersing agent of the type described in the patents to Keil, cited supra, and (3) a non-ionic surfactant having an HLB number greater than 10. This invention is said to provide an effective and cost efficient foam control method for the non-aqueous systems described. A similar composition containing a high molecular weight polydimethylsiloxane was also shown to be useful in defoaming highly acidic aqueous systems by Schiefer in U.S. Pat. No. 4,762,640.
Aizawa et al., in U.S. Pat. No. 4,639,489 and U.S. Pat. No. 4,749,740, the disclosures of which are hereby incorporated by reference, teach a method for producing a silicone defoamer composition wherein a complex mixture of polyorganosiloxanes, filler, a resinous siloxane and a catalyst to promote reaction of the other components are heated together at 50.degree. C. to 300.degree. C.
More recently, a method for preparing a composition similar to that described by Aizawa et al., cited supra, was disclosed in Australian Patent Application No. 75771/87, published on Jan. 21, 1988 and assigned to Dow Corning KK, the disclosure of which is hereby incorporated by reference. In this disclosure, the abovementioned complex silicone mixture additionally contains at least 0.2 weight parts of an organic compound having at least one group selected from COR, --COOR' or --(OR").sub.n --, wherein R and R' are hydrogen or a monovalent hydrocarbon group, R" is a divalent hydrocarbon group having 2 to 6 carbon atoms and the average value of n is greater than one. In this disclosure the inventor, T. Miura, emphasizes the need to react all the ingredients, including a catalyst, at elevated temperature to obtain the desired antifoam agent.
John et al., in European Patent Application No. 217,501, published Apr. 8, 1987, the disclosure of which is hereby incorporated by reference, discloses a foam control composition which gives improved performance in high foaming detergent compositions which comprises (A) a liquid siloxane having a viscosity at 25.degree. C. of at least 7.times.10.sup.-3 m.sup.2 /s and which was obtained by mixing and heating a triorganosiloxane-endblocked polydiorganosiloxane, a polydiorganosiloxane having at least one terminal silanol group and an organosiloxane resin, comprising monovalent and tetravalent siloxy units and having at least one silanol group per molecule, and (B) a finely divided filler having its surface made hydrophobic. John et al. further describes a method for making the foam control compositions and detergent compositions containing said foam control compositions.
Starch, in U.S. Pat. No. 4,983,316 discloses a dispersible antifoam composition for providing controlled foaming liquid laundry detergent formulations and wherein there is provided a non-aqueous emulsion of primary and secondary silicone antifoam agents, at least one nonionic silicone surfactant for emulsifying the primary and secondary antifoaming agents in a solvent, a first organic surfactant dispersing agent for assisting in dispersing the emulsified primary and secondary antifoaming agents in the liquid laundry detergents, and a second dispersing agent of a nonionic difunctional block-copolymer terminating in primary hydroxyl groups for further assisting in dispersing the emulsified primary and secondary antifoam agents in the liquid laundry detergent. A liquid laundry detergent composition containing the composition described immediately above is also disclosed. Starch, in U.S. Pat. No. 4,978,471 discloses a composition which contains essentially the same components as in the '316 patent, however in the '471 patent the secondary antifoam agent is a blend of a polydimethylsiloxane substituted with polar groups and a polydimethylsiloxane fluid.
Terae et al., in U.S. Pat. No. 4,690,713, discloses an antifoam composition comprising (a) 100 parts by weight of a hydrocarbon oil, such as a spindle oil or silicone fluid (e.g. a polydimethylsiloxane fluid having a viscosity of 20 to 1,000,000 centistokes at 25.degree. C., (b) 0.1 to 40 parts by weight of an organosilane compound having 1 to 3 hydroxy groups or hydrolyzable groups (such as alkoxy, acyloxy, and alkenyloxy groups), (c) 1 to 40 parts by weight of a finely divided silica powder and optionally a catalyst.